fft_amp

1 Description
2 Syntax
3 Parameters
4 Return
5 Examples
6 Remark
7 See Also
8 Header to Include
9 Reference

Description

Calculate frequency and amplitude.

Syntax

void fft_amp(vector &vx, vector &vy, vector &vfreq, vector &vAmp, int nSize, bool bNormalize = false, bool bOneSide = true)

Parameters

vx: [input] buffer containing time
vy: [input] buffer containing signal
vfreq: [output] the result of the frequency
vAmp: [output] the result of the amplitude
nSize: [input] size of the input data
bNormalize: [input] normalize the out amplitude or not
bOneSide: [input] output one-sided amplitude or not

Return

None

Examples

Prior to compilation, load fft_utils.c to the workspace by executing the following LabTalk command:

Run.LoadOC("Originlab\fft_utils.c", 16);

To retain fft_utils.c in the workspace for successive sessions, drag and drop the file from the Temporary folder to the System folder.

EX1

//Before running this example, import \\Samples\Signal Processing\fftfilter1.DAT to worksheet
#include <fft_utils.h>
void fft_amp_ex2()
{
    Worksheet wks = Project.ActiveLayer();
    if( wks )
    {   
        Column colX(wks, 0);
        Column colY(wks, 1);
        if( colX && colY )
        {
        
            XYRange rng;
            rng.Add(wks, 0, "X");
            rng.Add(wks, 1, "Y");
            
            vector vX, vY;
            rng.GetData(vY, vX);
            int nSize = vX.GetSize();   
            
            // prepare frequcy and amilitide columns
            Column colFreq(wks, wks.AddCol());
            colFreq.SetLongName("Frequency");
            
            Column colAmp(wks, wks.AddCol());
            colAmp.SetLongName("Ampilitude");
            
            vector& vFreq = colFreq.GetDataObject();
            vector& vAmp = colAmp.GetDataObject();
            
            // to calculate frequcy and ampilitude
            fft_amp(vX, vY, vFreq, vAmp, nSize); 
            
            // plot 
            GraphPage gp;
            gp.Create("origin");
            
            GraphLayer gl = gp.Layers(0);   
            Curve cv(wks, colFreq.GetIndex(), colAmp.GetIndex());
            gl.AddPlot(cv);
            gl.Rescale();   
        }
    }
}